1. Field of the Invention
The present invention relates to a vehicle air-conditioning system having a compressor of a refrigerant cycle, driven by a vehicle engine or an auxiliary driving unit such as an electrical motor. The vehicle air-conditioning system improves cooling performance even when operation of the compressor is forcibly temporarily stopped.
2. Description of Related Art
In recent years, for protecting the environment, a vehicle such as an eco-run vehicle or a hybrid vehicle, where a vehicle engine automatically stops when the vehicle is halted for example at a traffic signal, is practically used.
However, in a vehicle air-conditioning system, a compressor of a refrigerant cycle is driven by the vehicle engine. Therefore, when the vehicle engine is stopped when the vehicle is halted for example at a traffic signal, temperature of air blown from an evaporator is increased with the compressor stoppage, and temperature of air blown into a passenger compartment is increased.
A Further, even when the vehicle engine operates, the operation of the compressor may be forcibly temporarily stopped by a request from a vehicle engine side. For example, when the vehicle is accelerated, the operation of the compressor is forcibly temporarily stopped so that accelerating performance of the vehicle is improved. In this case, when the operation of the compressor is forcibly temporarily stopped, the temperature of air blown into the passenger compartment is increased, and cooling performance for a passenger in the passenger compartment is deteriorated.
In a conventional compressor control system described in JP-U-2-114511, when a vehicle is decelerated, the compressor is forcibly operated, and an evaporator is forcibly frosted. Therefore, during the vehicle decelerating, cold is stored in the evaporator as latent heat. When the vehicle is stopped after the vehicle decelerating, air passing through the evaporator can be cooled using the cold stored in the evaporator while the compressor is stopped. However, in the conventional system, because cold-storing is only performed within a short time during the vehicle decelerating, cold is not always stored in the evaporator. As a result, the cooling performance for the passenger is deteriorated when the operation of the compressor is forcibly temporarily stopped based on a request of the engine side.